HD 15337 c
Astrophysical Synthesis & Habitability Characterization
HD 15337 c is a confirmed sub-neptune exoplanet orbiting the star HD 15337, located approximately 146.2 light-years (44.82 parsecs) from the Solar System. First announced in 2019 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0734% across the stellar disk), this world measures 2.526 Earth radii and has a measured mass of 6.792 Earth masses. Combining its mass and radius yields a mean bulk density of 2.32 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 18.3 km/s.
In its orbital architecture around HD 15337, HD 15337 c completes one full revolution every 17.181 Earth days at a semi-major axis of 0.1235 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 78.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.096 carries the world between 0.1116 AU at periapsis and 0.1354 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 656 K (+383°C / +721°F) and receiving 45.07 S⊕ (~61,338 W/m²), HD 15337 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 15337 is classified as an orange K-type star of spectral type K1 V with an effective photospheric temperature of 5,131 K, a radius of 0.855 R☉, a mass of 0.829 M☉, an estimated bolometric luminosity of 0.455 L☉. Stellar evolution modeling indicates an estimated stellar age of 9.6 Gyr and a metallicity of [Fe/H] = 0.03 dex (near-solar heavy-element abundance). From Earth, HD 15337 shines at apparent V-band magnitude 9.1 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 15337 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 15337 c sharing its stellar neighborhood alongside HD 15337 b.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 15337 |
| Spectral Type | K1 V |
| Effective Temp (Teff) | 5,131 K |
| Stellar Radius | 0.8550 R☉ |
| Stellar Mass | 0.8290 M☉ |
| Bolometric Luminosity | 0.455 L☉ |
| Metallicity [Fe/H] | 0.030 dex |
| Stellar Age | 9.600 Gyr |
| Apparent Magnitude | V: 9.100 · G: 8.856 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.123500 AU |
| Orbital Period | 17.181 days |
| Mean Orbital Velocity | 78.2 km/s |
| Orbital Eccentricity (e) | 0.09600 |
| Orbital Inclination (i) | 88.4100° |
| Mean Bulk Density | 2.32 g/cm³ (18.3 km/s vesc) |
| Insolation Flux | 45.0685 S⊕ (~61,338 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 146.200 LY (44.816 pc) |